Artifical joint prosthesis using Al{hd 2{b O{HD 3{B {0 material

ABSTRACT

Prosthesis made of biologically compatible material, such as Al2O3, can be directly implanted in bone tissue without cement and without biologically deleterious effects. At least one surface is provided by means of which the load forces are transmitted directly between the prosthesis and the bone tissues. A socket may be polygonally shaped, or may be cylindrical with a helically exterior screw thread. Exterior grooves are provided, into which bone tissue grows to firmly bond the prosthesis in place and means is provided to prevent rotation prior to bone tissue growth.

United States Patent [191 Heimke et al.

[ Dec. 9, 1975 ARTIFICAL JOINT PROSTHESIS USING A1 0 MATERIAL [75]Inventors: Gunther Heimke, Mannheim; Peter Griss, Plankstadt; HannsFrhr. von Andrian-Werburg, llvesheim, all of Germany [73] Assignee:Friedrichsfeld GmbH Steinzeug-und Kunststoffwerke, Mannheim, Germany[22] Filed: May 3, 1974 [21] Appl. No.: 466,640

[30] Foreign Application Priority Data May 17, 1973 Germany 2324865 May19, 1973 Germany 2325585 [52] US. Cl 3/1-912; 3/l.913; 128/92 C; 128/92CA [51] Int. Cl. A61F l/24 [58] Field of Search 3/1, 1.9-1.913; 128/92C, 92 CA, 92 R, 92 BC [56] References Cited UNITED STATES PATENTS2,668,531 2/1954 Haboush 128/92 CA 3,774,244 11/1973 Walker 3/1 FOREIGNPATENTS OR APPLICATIONS 2,096,895 3/1972 France 128/92 C OTHERPUBLICATIONS Replacement of Arthritic Hips by the McKee-FarrarProsthesis by G. K. McKee et al., The Journal of Bone & Joint Surgery,Vol. 48 B, No. 2, pp. 245 & 246, May 1966.

The Trapezoidal 28 from Zimmer USA (Advertisement) 3 pages relied uponThe Journal of Bone & Joint Surgery, Vol. 55-A, No. 3, Apr. 1973.

F. R. Thompson Hip Prosthesis Vitallium Surgical Appliances, (catalog),ustenal Medical Div. Howmet Corp., New York, N.Y., 1964, pp. 23-24.

Switzerland 3/1 France 128/92 C Primary Examiner-Ronald L. Frinks [57]ABSTRACT Prosthesis made of biologically compatible material, such as A10 can be directly implanted in bone tissue without cement and withoutbiologically deleterious effects. At least one surface is provided bymeans of which the load forces are transmitted directly between theprosthesis and the bone tissues. A socket may be polygonally shaped, ormay be cylindrical with a helically exterior screw thread. Exteriorgrooves are pro vided, into which bone tissue grows to firmly bond theprosthesis in place and means is provided to prevent rotation prior tobone tissue growth.

14' Claims, 9 Drawing Figures US. Patent Dec. 9 1975 Sheet 1 of23,924,275

a wmw l- US. Patent Dec. 9 1975 Sheet 2 of 2 3,924,275

1 ARTIFICAL JOINT PROSTHESIS USING A1203 I MATERIAL The inventionrelates to a socket for a hip joint prosthesis of ceramic material forimplantation without cement.

The hip joint prostheses used hitherto generally consist of plasticsockets and a metal part for the replacement of the head of the femur,or of metal sockets and a plastic part as a replacement of the head ofthe femur. These parts and especially the sockets, hitherto were mostlyanchored and fixed in the hip bone with bone cement.

Hip joint prostheses made of ceramic, especially of a compactaluminum-oxide-ceramic, have also been proposed already. These ceramicprostheses have the advantage, as compared to the metal andmetal-plastic combination prostheses, that the friction, gliding andwear characteristics of ceramic, especially of aluminum oxide ceramic,are much superior to those of the metals and plastics. Moreover theceramic has a much better body compatibility than plastics and metals.

in order to be able to utilize this greater body compatibility of theceramic implants, it is however necessary, to implant and secure themwithout the use of plastic cements. The sockets of hip joint prosthesesused hitherto for implantation without cement, consisted essentially inimitations of the socket shapes, which had been known from plasticsocket constructions. The surface facing the bone, was generallyessentially hemispherical or cup shaped and had grooved patterns ofvarious kinds. The disadvantage of this construction consisted in thefact that for a firm anchoring in the bone, either complicated puncturepatterns had to be chiselled into the hip bone, or else the growing ofbone into the grooved structure took some time, so that patients wereexposed to a relatively long period of immobilization. This is howeverundersirable because of the danger of thrombosis.

In the case of the metal sockets for hip joint prostheses, a screw-typefastening is already known. (Total endoprosthesis according to Ring). Inthe case of this construction, however, the overall height amounts toseveral times the diameter of the socket, the diameter of the thread isconsiderably smaller than the diameter of the hemispherical cavity ofthe socket. This construction however, can not be used for a ceramicsocket, especially one of compacted aluminum-oxide-ceramic, since itdoes not take into consideration the material characteristics of ceramicand since there would be the danger of breaking of the long screw duringfastening.

According to the present invention, the construction described in thefollowing pages in more detail, and which at the same time has a numberof advantages, is provided for the socket of hip joint prostheses madeof aluminum-oxide-ceramic. It has been discovered that the socket of theinvention will permit a load to be applied, even in case of cement-freeimplantation, very soon after the operation and nevertheless grows veryfirmly into the body even in the succeeding period, while under strain,and is completely integrated into the bone connection mechanism.

Sockets made of various metal alloys for cement-free implantation havealso been proposed already. Screws or else long pegs served for theirattachment, which are screwed or driven into the adjacent bone space.

However it turned out that the bio tolerance of plastic cements,plastics and metals is not very favorable.

Therefore, the danger exists of a loosening of the socket after thecemented-in socket has remained in the body for some time. This dangerof loosening is particularly great in case of the metallic socketsimplanted without cement.

For some time it has been known, that certain types of ceramic and a fewtypes of glass ceramic have a considerably more favorable bodycompatibility as compared to metals and plastics. This is particularlytrue for A1 0 ceramic, whereby we understand by A1 0 ceramic, a ceramicwhich contains aluminum-oxide or more, especially 99% A1 0 Extensiveanimal experiments and first results of cement-free implantations ofparts of joint prostheses made of compact A1 0 ceramic, show that a firmanchoring of such parts without the help of cement is possible. In caseof favorable conditions, for example, after an immobilization of therespective joint for a few weeks to months, a mechanically very strongconnection develops between the implant and the surrounding bone tissue.

For the cement-free implantation of hip joint sockets for totalprostheses made of A1 0 ceramic, sockets of various other shapes havealso been proposed and used already; one socket construction of thistype has at its rear an essentially hemispherical shape, into which deepgrooves have been worked in. It carries a peg at its crest, which isround and which likewise has deep grooves. This socket construction issimilar to known sockets made of plastic and, in case of cement-freeimplantation, it hasthe disadvantage that there is no genuine protectionagainst twisting. Until such time that the tissue has grown firmly tothe surface, or the bone tissue has grown into the grooves and channels,there exists the danger of twisting of this type of socket in case ofeven slight movement in the joint, as a result of which this growing-in,or -on, can be delayed or even prevented.

One form of socket for total hip joint prostheses made of A1 05,ceramic, according to the invention for cement-free implantation, has anangular shaped rear portion. It can be triangular, square, pentagonal orhexagonal. This angular rear portion is provided with grooves andchannels, a part of which can also have some dovetailed or similarreverse tapering, and can grow into the bone tissues for a betteranchoring of the socket.

The invention also relates to the thigh part of a total hip jointprosthesis for the cement-free implantation, especially prosthesesconsisting of A1 0 ceramic and prostheses made of a combination of aceramic head with a metal shaft, in which case, the metal shaft iscovered with a vitreous material such as a glaze, enamel or a glassceramic, as described and claimed in the copending application ofGunther F. A. Heimke and Peter Griss, Ser. No. 440,444, filed Feb. 7,1974, corresponding to German Application No. P 23 06 552.3.

The thigh parts of total hip joint prostheses are attached, at present,mostly by means of plastic cement in the marrow space of the femur.These prostheses consist of metal alloys, the composition of which isselected such that they will show the least possible corrosion phenomenain a biological environment. The transfer of a load from the thighprosthesis to the femur takes place in the case of these prosthesesessentially by the intermediation of the bone cement, which in itsplastic state, closely follows the inside contour of the femur. Duringshaping the shaft of a metal thigh prosthesis for implantation with theaid of bone cement, no

special attention need be given to the load transfer from the prosthesisto the femur. Since this part of the prosthesis is surrounded entirelyby bone cement, aspects of tissue tolerance and avoiding of movementsbetween bone tissue and the implant are of no consequence during shapingof said part. Therefore, in case of the metal prostheses forimplantation with plastic cements, one needs to consider only mechanicalaspects for the shaping of the shaft of the prosthesis.

Prior to the general introduction of bone cements for the attachment ofjoint prostheses in the adjacent bone space, it was also customary tointroduce or drive into the marrow space of the femur thigh parts of hipjoint prostheses even without bone cement. This method of attachmenthowever, was unsatisfactory. In many cases these parts of prosthesessunk deeper and deeper into the femur, since the bone decomposed inareas where the load was too high. In many other cases, the prosthesisbecame loose after a time, since a firm connection between the shaft ofthe prosthesis and the bone tissue did not occur because of theunfavorable biological tolerance of the metals.

Because certain types of ceramic, for example compacted A1 ceramic with99% A1 0 content, as well as certain glass ceramics have an excellenttissue compatibility, especially in regard to bone tissue, it has beenfound that under certain conditions, a mechanically firm connectionbetween the surfaces of such implants and the bone tissue develops.

This now results in the possibility of anchoring the thigh parts oftotal hip joint prostheses without cement and mechanically solidly inthe marrow space of the femur. This cement-free implantation is verydesirable, since the plastic bone cements available hitherto had manyand serious drawbacks.

However, up to now there did not exist any prosthesis constructions forthis cement-free implantation, in the case of which the introduction ofthe load from the implant into the femur is accomplished in such a way,that bending and tension strains in the adjacent surfaces between theimplant and the bone are avoided as much as possible, and high pressureloads are eliminated. In the case of the use of total ceramicprostheses, one must naturally also take the characteristics of compactA1 0 ceramic into consideration.

Other objects and advantages will be apparent to those skilled in theart by reading the following specification in connection with theannexed drawings, in which;

FIG. 1 is a cross-section of a preferred form of hip joint socket madein accordance with the invention;

FIG. 2 is a fragmentary cross-section of a detail of FIG. 1;

FIG. 3 is a top view of the socket;

FIG. 4 is a cross-section of a modified form of socket;

FIG. 5 is a bottom view of the socket of FIG. 4;

FIG. 6 is a top view of the socket of FIGS. 4 and 5;

FIG. 7 is a side elevation of a preferred form of the thigh portion ofthe prosthesis;

FIG. 8 is a side elevation as viewed from the left of FIG. 7, and

FIG. 9 is a cross-section on the line 9-9 of FIG. 8.

A socket made in accordance with a preferred form of the invention madeof aluminum-oxide-ceramic for implantation without cement will beexplained in more detail on the basis of FIGS. 13. FIG. 1 shows asection through the socket; FIG. 2 the anchoring thread and FIG. 3, aview of the socket from above. The socket contains the approximatelyhemispherical cavity 1, the surface of which is polished and on whichthe spherical head, likewise polished on its surface and consisting ofthe same ceramic, of the thigh element of the hip joint prosthesis,anchored in the femur, is mounted in a swivel-type manner. The body ofthe socket consists of aluminum-oxide-ceramic 2. According to theinvention, this socket body is cylindrically-shaped in its upper partwhich faces the hip bone, with a cylinder diameter D, which is smallerthan the total diameter d l of the socket, but larger than the diameterof the hemispherical cavity d 2 in the inside of the socket. The overallheight h of the socket according to the invention is smaller than thediameter of the hemispherical cavity d 2.

The cylindrical part of the socket is provided on its outside surfacewith a thread 3. This thread 3 is made in such a manner that it cantransfer forces, which act from the thigh on the socket, particularlyfavorably to the hip bone. These forces are, directed from below toabove in the representation shown in FIG. 1. An example for a threadmade in this way is shown in FIG. 2. On the outside of the cylindricalpart having the diameter D, axially parallel grooves are worked intransverse to the thread. These grooves can be of a semicircular shapefor example. They are designated by 4 in FIG. 3, which shows a view ofthe socket from above. These grooves interrupt the thread, whereby itappears to be particularly useful, to make this break as sharp-edged aspossible. In FIG. 3, four such grooves have been drawn but, their numbercan also be greater or smaller than four. In the extension of thesegrooves there are holes which extend through the bead-shaped part 5 ofthe socket up to the front side of the socket. On the topside of thesocket, that is, of the side projecting into the hip bone, a series ofgrooves is provided. In FIG. 1, these grooves consist of the dove-tailedgrooves 6 and 7, which, in the view of FIG. 3, are represented by thegrooves 8. Naturally, other arrangements of the grooves may also beselected according to the invention, but it will be particularly usefulto provide the grooves existing on the topside with reverse-tapering, asgiven by the dovetail of the grooves 6 and 7. In the middle of thesocket cavity, a hole 9 is provided.

During implantation of the socket according to the invention, for hipjoint prostheses, one proceeds as follows: first an approximately roundpart is chiselled out, having a diameter which is still noticeablysmaller than the diameter of the cylindrical part of the socket. Itsdepth is chiselled out to the point which approximately corresponds tothe later seat of the socket. Subsequently, the preprocessed cavity isfiled out further with a rasp, the diameter of which, measured acrossthe outside teeth of the rasp, corresponds to the diameter D less twicethe depth t of the thread. In the wall of this cylindrical hole, athread is cut with a suitably shaped set of threading tools into the nowcylindrical wall of the bone. At the same time the threading tool isdimensioned such that, after the last cutting process, the thread isabout /2 to 1mm smaller in its diameter, than would correspond to thethread on the socket.

The grooves 6 and 7 or 8 are partly filled with the bone ships producedduring the chiselling out of this cavity. Then the socket is moved closeto pre-cut turns of the thread and is turned into the preprocessedthread with a tool which reaches into the continuous holes 4 or theirextensions. Since the pre-cut thread was a little smaller thancorresponds to the thread of the socket,

the application of some force is necessary for this, as a result ofwhich, the socket thread forces itself firmly into the bone. Thisforcing into "is assisted by the four grooves 4, which cut the thread.This assistance is the more favorable, the more sharp-edged these breaksare, as has already been explained further back.

By this screwing in of the sockets into av somewhat smaller thread, thesocket will be firmlyanchored in the hip bone immediately after.implantation. At the same time, it has been discovered to beparticularly favorabl'e, surprisingly, that the bone particles whichwere still separated during this's'crewing in,'collect and remain in thegrooves 4; It'also turns out, that these bone chips collecting" thereconsiderably favor the growing-in of the livebone into'the spaces 4.

After screwing in of the socket, it will be desireable to drill a holeofabout half the socketheight from the outside witha drill inserted intoat least one of the holes, which are located in extensions ofthe'grooves4. A ceramic peg is pushed into this hole, the outside diameter of whichcorresponds to the inside diameter of these holes, and the length ofwhich is similarto half the height of the socket. This peg serves as ,anadditional protection against twisting until the socket has completelygrown in.

The hole 9 serves for one thing, for letting the air, which iscompressed during screwing in of the socket, escape, and for another,for the improvement of the admittance of synovia into the hemisphericalcavity of the socket during subsequent use of the joint.

The construction of the socket for hip joint prostheses made ofaluminuin-oxide-ceramic, according to the invention, thus has theadvantage that it results in a after the implantation, so that it canwithstand a strain very soon after the operation/Beyond that, it causesan acceleration of the growing-in process "into the bone tissue, wherebythe'well known stimulation of the adhesion of bone tissue to thealuminum-oxide-ceramic will be favored additionally throughthe presenceof bone particles belonging to its own body, precisely at those placeswhere the growing together is particularly desirable for the attachmentof the prosthesis.

Another form of socket according to the invention is shown in FIGS. 4and 5 in the form of a square socket. This socket consists of a socketbody 11, the inside of which contains the approximately hemisphericalhollow space 12, in which the complementary shaped head of the thighpart of the total prosthesis is seated. The rear 13 of this prosthesisis made square as the top view shown in FIG. 6 shows. On the side, thesocket has grooves 14. Grooves and indentations are also worked into therear, which are designated by 15 and 16 in FIG. 6. Part of these groovesin FIGS. 4 and 6, the grooves designated by 16, have reverse tapers.Such grooves, channels or other indentations serve for the purpose ofanchoring the socket firmly by means of growing-in tis sue in theadjacent bone space. These grooves, channels and indentations can befilled with bone chips from the same patient during the operation andprior to the insertion of the socket in the hip bone.

Various polygonal configurations for the socket body can be used, but incase of square, pentagonal or hexagonal sockets, at least one corner onthe front of the socket may be bevelled in order to avoid a chafing ofthe iliopsoas. This bevelling is designated by 17 in the lower part ofFIG. 5 for a square socket.

The socket according to this modification of the invention, has theadvantage, as compared to hitherto known sockets made of A1 0 ceramic,that it can be inserted without a special set of instruments. The spaceneeded for the socket in the hip bone, can be worked out and preparedwith'the instruments customary in orthopedic surgery. Imp'lantations ofsockets of this type into large animals, such as sheep, have shown thatthese sockets havesuch'a firm seat immediately after implantation, thatthey'will not become loose even in the case of an immediateload on thejoint, but that a mechanically firm connection develops with thesurrounding bone tissue. a Q I A preferred form of construction for thethigh part of a hip joint prosthesis isv shown in FIGS. v7.9, in whichthe prosthesis is made of compacted A1 0 ceramic. It consists of thespherical head 21, the transition part 22 with the collar 23 and theshaft 24. FIG. 8 shows a view of the same prosthesis viewed from theside of. the center of curvature pof the shaft 24. The prosthesis issupported by the surface, designated by '25, and with the fillet thereon the front side of the wall of the femur. It is favorable to make thissurface 25 as broad as possible, in order 'to avoid any increase inpressure during introduction of the load from the prosthesis to thefemur. The corresponding surface on the reverse side 26; the side facingaway from the center of curvature of the shaft of the prosthesis, merelyhas to have the width which is required for reasons of strength. Thewidths of the shaft of the prosthesis at its upper end at the pointwhere it joins surfaces '25 and 26, should therefore ei-, ther be thesame on both sides, or else the width on side 25; on the side facing thecenter of curvature, should be larger than on side 26, which is the sidefacing away from the center of curvature. At the same time, experienceshows it to be particularly advantageous to select the width on the sideof the shaft of the prosthesis, facing the center of curvature, to be nosmaller than 10mm. According to the invention, the downward tapering; ofthe shaft of the prosthesis is accomplished ,in such a manner, that thewidth on the side facing the center p of the curvature decreases morerapidly than on the side facing away from said center of curvature. Inthe lower part of the shaft, about at the level 27 of the FIG. 8, thewidth on the inside, that is, on the side facing the center ofcurvature, is smaller than on the outside of the shaft facing away fromthe center of curvature. Here, the width on the inside can amount tobetween 5 and 7mm and, on the outside, to between 8 and 9mm. The ratiobetween the inside and outside widths at the upper end of the shaftshould be about 1.0 to 1.0. At the lower part of the shaft of theprosthesis, the ratio should however, be at the most 0.9 to 1.0.

In animal experiments and in experiments where the load transmissionratios were simulated as they exist in the human body, it turned outthat prostheses according to the invention, are capable of bearing theusual overall loads without, at the same time, incurring pressures atany places which are higher than those corresponding to the pressureload in the natural bone. Thus, in the case of use of the prosthesisaccording to the invention, there is no danger of degeneration of thebone as a result of pressure necrosis.

As in the case of the sockets made of A1 0 ceramic, the shaft of thethigh portion of the prosthesis made from this material will, over aperiod of time, become securely fixed within the femur due to theaffinity of this ceramic for the growing tissues. and because theceramic is biologically compatible with these tissues.

We claim:

1. A socket for hip joint prostheses for cement-free implantation inbone tissue, comprising a biologically compatible material such ascompacted A1 ceramic, said socket being provided with an internalhemispherical cavity, an exterior upper load bearing surface portion ofthe socket being provided with at least one elongated groove to providea direct physical connection with bone tissue grown after implantationand an exterior surface portion including means to prevent rotation ofthe socket directly after implantation, the overall height of the socketbeing less than the diameter of the hemispherical cavity, the transversedimensions of the upper portions of the socket being less than thelargest diameter of the socket but, larger than the diameter of thehemispherical cavity.

2. The invention defined in claim 1, wherein the upper exterior surfaceof said socket is provided with at least one groove having an undercuttransverse profile to receive bone tissue grown after implantation.

3. The invention defined in claim 1, wherein an upper exterior surfaceof said socket is defined by a cylinder of revolution, and saidelongated groove comprises a helical thread provided in said exteriorsurface.

4. The invention defined in claim 3, wherein the transverse profile ofsaid thread includes one face disposed generally normal to the directionof the force of the load to be supported by the socket.

5. The invention defined in claim 3, wherein said means to preventrotation comprises at least one elongated groove provided in said uppersurface, and transversely intersecting at least some of the turns ofsaid thread.

6. The invention defined in claim 3, wherein said socket is providedwith a bore extending between the interior of the cavity and the upperexterior surface of the socket.

7. The invention defined in claim 3, wherein said socket includes anannular flange flaring outwardly from the hemispherical cavity.

8. The invention defined in claim 7, wherein said means to preventrotation comprises a peg to be inserted in an axial direction through anopening provided in said annular flange and the bone tissue in alignmenttherewith.

9. The invention defined in claim 7, wherein the transverse profile ofsaid elongated groove intersecting said threads is defined by asemi-cylindrical surface in axial alignment with said opening in theannular flange.

10. A socket for hip joint prostheses for cement-free implantation inbone tissue, comprising a biologically compatible material such ascompacted A1 0 ceramic, said socket being provided with an internalhemispherical cavity, an exterior upper load bearing surface portion ofthe socket being provided with at least one elongated groove to providea direct physical connection with bone tissue, grown after implantationand an exterior surface portion including means to prevent rotation ofthe socket directly after implantation, the overall height of the socketbeing less than the diameter of the hemispherical cavity, the transversedimensions of the upper portions of the socket being at leastsubstantially equal to the largest diameter of the socket and largerthan the diameter of the hemispherical cavity, the exterior side surfaceof at least the upper portion of said socket being defined by a seriesof intersecting planes.

11. The invention defined in claim 10, wherein a lower portion of theexterior surface of the socket is defined by a plane intersecting anadjacent pair of said first mentioned planes and angularly relatedthereto.

12. The invention defined in claim 10, wherein said intersecting planesdefine a regular polygon:

13. The invention defined in claim 12, wherein said regular polygon hasfour sides.

14-. The invention defined in claim 13, wherein a lower portion of theexterior surface is defined by a plane intersecting an adjacent pair ofsaid first mentioned planes and angularly related thereto.

1. A SOCKET FOR HIP JOINT PROSTHESES FOR CEMENT-FREE IMPLANTATION INBONE TISSUE, COMPRISING A BIOLOGICALLY COMPATIBLE MATERIAL SUCH ASCOMPACTED AL2O3 CERAMIC, SAID SOCKET BEING PROVIDED WITH AN INTERNALHEMISPHERICAL CAVITY, AN EXTERIOR UPPER LOAD BEARING SURFACE PORTION OFTHE SOCKET BEING PROVIDED WITH AT LEAST ONE ELONGATED GROOVE TO PROVIDEA DIRECT PHYSICAL CONNECTION WITH BONE TISSUE GROWN AFTER IMPLANTATIONAND AN EXTRIOR SURFACE PORTION INCLUDING MEANS TO PREVENT ROTATION OFTHE SOCKET DIRECTLY AFTER IMPLANTATION, THE OVERALL HEIGHT OF THE SOCKETBEING LESS THAN THE DIAMETER OF THE HEMISPHERICAL CAVITY, THE TRANSVERSEDIMENSIONS OF THE UPPER PORTIONS OF THE SOCKET BEING LESS THE LARGESTDIAMETER OF THE SOCKET BUT, LARGER THAN THE DIAMETER OF THEHEMISPHERICAL CAVITY.
 2. The invention defined in claim 1, wherein theupper exterior surface of said socket is provided with at least onegroove having an undercut transverse profile to receive bone tissuegrown after implantation.
 3. The invention defined in claim 1, whereinan upper exterior surface of said socket is defined by a cylinder ofrevolution, and said elongated groove comprises a helical threadprovided in said exterior surface.
 4. The invention defined in claim 3,wherein the transverse profile of said thread includes one face disposedgenerally normal to the direction of the force of the load to besupported by the socket.
 5. The invention defined in claim 3, whereinsaid means to prevent rotation comprises at least one elongated grooveprovided in said upper surface, and transversely intersecting at leastsome of the turns of said thread.
 6. The invention defined in claim 3,wherein said socket is provided with a bore extending between theinterior of the cavity and the upper exterior surface of the socket. 7.The invention defined in claim 3, wherein said socket includes anannular flange flaring outwardly from the hemispherical cavity.
 8. Theinvention defined in claim 7, wherein said means to prevent rotationcomprises a peg to be inserted in an axial direction through an openingprovided in said annular flange and the bone tissue in alignmenttherewith.
 9. The invention defined in claim 7, wherein the transverseprofile of said elongated groove intersecting said threads is defined bya semi-cylindrical surface in axial alignment with said opening in theannular flange.
 10. A socket for hip joint prostheses for cement-freeimplantation in bone tissue, comprising a biologically compatiblematerial such as compacted Al2O3 ceramic, said socket being providedwith an internal hemispherical cavity, an exterior upper load bearingsurface portion of the socket being provided with at least one elongatedgroove to provide a direct physical connection with bone tissue grownafter implantation and an exterior surface portion including means toprevent rotation of the socket directly after implantation, the overallheight of the socket being less than the diameter of the hemisphericalcavity, the transverse dimensions of the upper portions of the socketbeing at least substantially equal to the largest diameter of the socketand larger than the diameter of the hemispherical cavity, the exteriorside surface of at least the upper portion of said socket being definedby a series of intersecting planes.
 11. The invention defined in claim10, wherein a lower portion of the exterior surface of the socket isdefined by a plane intersecting an adjacent pair of said first mentionedplanes and angularly related thereto.
 12. The invention defined in claim10, wherein said intersecting planes define a regular polygon.
 13. Theinvention defined in claim 12, wherein said regular polygon has foursides.
 14. The invention defined in claim 13, wherein a lower portion ofthe exterior surface is defined by a plane intersecting an adjacent pairof said first mentioned planes and angularly related thereto.